Chemical reaction profile combustion

It is denoted by C and depends on the flame temperature, mean molecular mass of the combustion products and propellant formulation. It is a fundamental parameter which gives the energy available on combustion and can be used to compare the efficiency of different chemical reactions independently of the Pc. For propellants, the value of C ranges between 1200 and 1600 ms-1. It is determined by firing a propellant grain in a motor and evaluating the area under the P-t profile and using Equation 4.11. 

The separation of the two sets of desorption products may indicate that they are from different sites. That is, branching of the selective and nonselec-tive oxidation takes place on adsorption of butene. This can be confirmed if the two sets of products can be varied independently. This is shown by two experiments. The first experiment makes use of the fact that butene and butadiene adsorb on the same sites. Butadiene is first adsorbed onto the catalyst (5). The catalyst is then heated to 210°C, desorbing all of the unreacted butadiene, but leaving on the surface the precursors of the combustion products. Since desorption of the unreacted butadiene does not involve a net chemical reaction, the adsorpton sites involved are not affected. The catalyst is then cooled to 22°C, and cis-2-butene is adsorbed. If selective oxidation and combustion take place on the same site, the adsorbed butene would undergo both reactions. If they take place on separate sites, and butene adsorbs only on the selective oxidation site (because the combustion site is covered by species from butadiene adsorption), the adsorbed butene would form only butadiene. Subsequent desorption yields a profile similar to that for a single adsorption of ds-2-butene (Fig.l, curve b). More importantly, within experimental errors, the amount of butadiene evolved is the same as in a ds-2-butene adsorption experiment, and the amount of C02 evolved is the same as in a butadiene adsorption experiment. Thus, the adsorbed butene forms only butadiene. These results show that under these experimental conditions (i.e., in the absence of gas-phase oxygen), the production of butadiene and carbon dioxide takes place on separate sites. 

Chemical reaction or reaction product, partly or entirely gaseous, that yields heat and light. State of blazing combustion. Flame profile is temperature profile of any particular flame. Flame temperature is the calculated or determined temperature of the flame. 

OSHA PEL TWA 0.5 mg(Ba)/m3 ACGIH TLV TWA 0.5 mg(Ba)/m3 Not Classifiable as a Human Carcinogen DFG MAK 0.5 mg(Ba)/m3 DOT CLASSIFICATION 6.1 Label KEEP AWAY FROM FOOD SAFETY PROFILE A poison via subcutaneous route. See also BARIUM COMPOUNDS (soluble). Combustible by spontaneous chemical reaction produces heat on contact with water or steam. Reacts with H2O, Ba(OH)2. Incompatible with H2S, hydroxylamine, N2O4, triuranium octaoxide, SO3. 

SAFETY PROFILE Moderately toxic by ingestion. Vapors are probably narcotic in high concentration. A skin and eye irritant. Combustible when exposed to heat or flame can react with oxidizing materials. Moderate explosion hazard by spontaneous chemical reaction. To fight fire, use CO2, dry chemical. See also ETHERS. 

CONSENSUS REPORTS Reported in EPA TSCA Inventory. Zinc and its compounds are on the Community Right-To-Know List. DOT CLASSIFICATION 4.2 Label Spontaneously Combustible SAFETY PROFILE Presumed to be a poison. Ignites spontaneously in air. Dangerously flammable by spontaneous chemical reaction in air, or with oxidizing materials. A dangerous explosion hazard. 

SAFETY PROFILE Moderately toxic by inhalation. Human systemic effects by inhalation general anesthetic, decreased pulse rate without blood pressure fall, and body temperature decrease. An experimental teratogen. Experimental reproductive effects. Mutation data reported. An asphyxiant. Does not bum but is flammable by chemical reaction and supports combustion. Moderate explosion hazard it can form an explosive mixture with air. Violent reaction with Al, B, hydrazine, LiH, LiC6Hs, PH3, Na, tungsten carbide. Also self-explodes at high temperatures. 

OSHA PEL TWA 0.1 mg(Tl)/m3 (skin) ACGIH TLV TWA 0.1 mg(Tl)/m3 (skin) SAFETY PROFILE Poison by ingestion, intraperitoneal, and intravenous routes. Combustible by chemical reaction. Evolves O2 875°. Mkmres with sulfur or... 

SAFETY PROFILE An inhalation hazard. Questionable carcinogen with experimental tumorigenic data by implant route. Combustible in the form of dust when exposed to heat or by spontaneous chemical reaction with Bra, BrFs, Cla, CIF3, Cu(N03), KaOa, S. See also POWDERED METALS and TIN COMPOUNDS,... 

DOT CLASSIFICATION 8 Label Corrosive SAFETY PROFILE Poison by intraperitoneal route. Moderately toxic by inhalation. A corrosive irritant to skin, eyes, and mucous membranes. Combustible by chemical reaction. Upon contact with moisture, considerable heat is generated. Violent reaction with K, Na, turpentine, ethylene oxide, alkyl nitrates. Dangerous hydrochloric acid is liberated on contact with moisture or heat. When heated to decomposition it emits toxic fumes of CL. See also HYDROCHLORIC ACID. 

This circumstance is often simpler to analyze, since the flame conditions are well established at the nozzle exit. There are then few subsequenf chemical reactions ahead of fhe farget surface. The tunnel burner is a common fully premixed burner. The gases are mixed and ignited inside the burner. They then travel through a refractory-lined chamber before leaving the burner. The combustion products may equilibrate inside the chamber. The temperature and composition are then uniform at the exit. However, the velocity profile may not be uniform. If may be approximately developed pipe flow, depending on fhe downstream length of the equilibration chamber. 

The temperature profile in the normal flame propagation of a combustible gas mixture is shown in Figure 2.6. dp is the thermal preparatory zone from the initial temperature of the mixture, To, to the temperature T[ required for starting the rapid chemical reaction is the chemical width of the flame front is the thermal width of the flame front between the temperature of ignition, Tf, and the temperature of steady burning, T. The section from T,- to T[ represents the induction period i. e. the period of acceleration of the oxidation (the horizontal axis of distance can be converted into time axis by the normal rate of flame propagation, w , directed toward the intact gas mixture). 

The equiHbrium approach should not be used for species that are highly sensitive to variations in residence time, oxidant concentration, or temperature, or for species which clearly do not reach equiHbrium. There are at least three classes of compounds that cannot be estimated weU by assuming equiHbrium CO, products of incomplete combustion (PlCs), and NO. Under most incineration conditions, chemical equiHbrium results in virtually no CO or PlCs, as required by regulations. Thus success depends on achieving a nearly complete approach to equiHbrium. Calculations depend on detailed knowledge of the reaction network, its kinetics, the mixing patterns, and the temperature, oxidant, and velocity profiles. 

The second is concerned with the need to have a complete and sensible chemical mechanism, valid over a wide range of temperature. Even a relatively simple combustion system will involve dozens of reactions, so that a well established reaction rate data base is essential. It is equivalently essential that the results be verified by comparison with detailed experimental data--such as that provided by laser probes. For example, in a study of the ozone decomposition flame (20). it was found that certain alternative but wrong choices of key input parameters were not discernible if flame speed were used as the sole predicted result for verification however, these choices did produce considerable differences in the profiles of the transient oxygen atom concentration and the temperature. 

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